Main chain selective polymer degradation: controlled by the wavelength and assembly

The advent of reversible deactivation radical polymerization (RDRP) revolutionized polymer chemistry and paved the way for accessing synthetic polymers with controlled sequences based on vinylic monomers. An inherent limitation of vinylic polymers stems from their all-carbon backbone, which limits both function and degradability. Herein, we report a synthetic strategy utilizing radical ring-opening polymerization (rROP) of complementary photoreactive cyclic monomers in combination with RDRP to embed photoresponsive functionality into desired blocks of polyvinyl polymers. Exploiting different absorbances of photoreactive cyclic monomers, it becomes possible to degrade blocks selectively by irradiation with either UVB or UVA light. Translating such primary structures of polymer sequences into higher order assemblies, the hydrophobicity of the photodegradable monomers allowed for the formation of micelles in water. Upon exposure to light, the nondegradable blocks detached yielding a significant reduction in the micelle hydrodynamic diameter. As a result of the self-assembled micellar environment, telechelic oligomers with photoreactive termini (e.g., coumarin or styrylpyrene) resulting from the photodegradation of polymers in water underwent intermolecular photocycloaddition to photopolymerize, which usually only occurs efficiently at longer wavelengths and a much higher concentration of photoresponsive groups. The reported main chain polymer degradation is thus controlled by the irradiation wavelength and the assembly of the polymers.


SEC-ESI-MS
Size exclusion chromatography coupled with electrospray ionisation mass spectrometry experiments were measured using a Q Exactive Plus Biopharma mass spectrometer (Thermo Fisher Scientific, San Jose, CA, USA) equipped with a HESI-II ionisation source.The mass spectrometer was calibrated up to m/z 2000 using premixed calibration solution (Pierce; Thermo Scientific) and for high mass mode (m/z 600-8000) using ammonium hexafluorophosphate solution.A constant spray voltage of +3.5 kV, a dimensionless sheath gas and a dimensionless auxiliary gas flow rate of 10 and 0 were applied, respectively.The capillary temperature was set to 320 °C, the S-lens RF level was set to 150 and the auxiliary gas heater temperature was set to 125 °C.The Q Exactive was coupled to an UltiMate 3000 UHPLC System (Dionex, Sunnyvale, CA, USA) consisting of a pump (LPG 3400SD), autosampler (WPS 3000TSL), and a temperature-controlled column department (TCC 3000).Separation was performed on two mixed bed size exclusion chromatography columns (Agilent, Mesopore 250 × 4.6 mm, particle diameter 3 µm) with a precolumn (Mesopore 50 × 7.5 mm) operating at 30 °C.THF at a flow rate of 0.30 mL min -1 was used as eluent.The mass spectrometer was coupled to the column in parallel with an UV-detector (VWD 3400, Dionex) and a Refractive Index detector (RefractoMax520, ERC, Japan) as described earlier. 1 A split flow of 0.27 mL min -1 of the eluent were directed through the UV-and RI-detector and the remaining 30 µL min -1 directed into the electrospray source following post-column addition of 50 µM sodium iodide in methanol at 20 µL min -1 by a micro-flow HPLC syringe pump (Teledyne ISCO, Model 100DM).A 100 µL aliquot of polymer solution at 2 mg mL -1 concentration was injected into the SEC system for analysis.

ESI-HRMS
The working solution was prepared from stock solution of analyte sample 0.05 mg mL -1 and methanolic solution of sodium acetate 0.2mM with the volume ratio of 10:2.The working solution was then infused directly to the MS system at constant flow rate of 5 μL min -1 via a 500 μL syringe controlled by a syringe pump (Pump 11 Elite, Harvard Apparatus).Spectra were recorded on the same Q Exactive Plus Biopharma mass spectrometer as described above for the SEC-ESI-MS experiments, operating in positive ion mode.A constant spray voltage of 3.0 kV, a dimensionless sheath gas and a dimensionless auxiliary gas flow rate of 25 and 10 were applied, respectively.The capillary temperature was set to 320 °C, the S-lens RF level was set to 60, and the auxiliary gas heater temperature was set to 100 °C.

THF-SEC
The SEC measurements were conducted on a PSS SECurity

NMR Measurements
1 H-and COSY spectra were recorded on a Bruker System 600 Ascend LH, equipped with a BBO-Probe (5 mm) with z-gradient (1H: 600.13 MHz, 13C: 150.90 MHz,).All measurements were carried out in deuterated solvents.The chemical shift (δ) is recorded in parts per million (ppm) and relative to the residual solvent protons. 2 The measured coupling constants were calculated in Hertz (Hz).To analyze the spectra the software

UV-VIS Spectroscopy
UV/vis spectra were recorded on a Shimadzu UV-2700 spectrophotometer equipped with a CPS-100 electronic temperature control cell positioner.Samples were prepared in THF and measured in Hellma Analytics quartz high precision cells with a path length of 10 mm at ambient temperature.

Dynamic Light Scattering Measurements
All dynamic light scattering (DLS) measurements were performed using a Malvern Zetasizer Nano-ZS instrument (Malvern Instruments) equipped with a backscattering detector (measurement angle = 175°).

Differential Scanning Calorimetry Measurement
DSC measurements were conducted using a Netzsch DSC 204 F1 Phoenix.Samples were dissolved in dichloromethane and dropped cast into DSC pans, followed by drying at 40 o C at high vacuum overnight prior to DSC measurement.3 cycles of heating/cooling ramps at scanning speed of 5 °C•min -1 were used over the temperature range from either 30 °C or -10 °C to 130 °C with isothermal exposures (10 min) at end temperatures.
A nitrogen sample purge flow of 20 mL•min -1 was employed.Glass transition temperatures were determined from the 2nd heating ramp.The data was analysed using the TA Instruments Universal Analysis 2000 software (version 4.2E).

Small-Angle Neutron Scattering Measurements
Static small-angle neutron scattering (SANS) measurements were obtained on the Bilby instrument, 3,4 in timeof-flight mode with an asymmetric detector array at the Australian Centre for Neutron Scattering (ACNS), ANSTO, Lucas Heights, NSW.A neutron wavelength of 4-14 Å was used in these measurements, obtaining a q-range of 0.0017-0.820Å −1 at a single instrument configuration.Distance to main detector, rear detector, horizontal curtains, and vertical curtains was 12m, 2m and 1m, respectively.Left, right, top, and bottom curtains separations from the beam were 0.20, 0.38, 0.10 and 0.25m, respectively.Source and sample aperture diameters were 40.0 and 12.5 mm.
Samples were prepared in 1 mm (limited by available amount of sample) path-length Hellma quartz cells for a bit more than two hours (8000 sec each).Best possible contrast (SLDpolymer = 0.9-1.1)was introduced by using D2O (SLD = 6.36) as the solvent.
SANS data reduction including placing data on the absolute scale was done using standard Bilby procedures implemented in Mantid. 5NS data was analysed using Primus software from ATSAS package 6 and also fit using Spherical polymer micelle model in SASView 5.0.5 [SasView 5.0.5.http://www.sasview.org/].

Degradation in DMAc with UV light
A quartz cuvette containing a solution of polymer in DMAc solvent (1 mg.mL -1 ) was placed in a Luzchem photoreactor equipped with 3 UV lamps.The cuvette was irradiated with UV light for certain amount of time which is specified in the result section.

Diblock polymer
1.5 mg of the polymer was dispersed in 1 mL of water.The dispersion was then filtered with 20 µm pore PTFE filter to remove any dust or unresolved solid fragment The dispersion was transferred to a quartz cuvette for photodegradation.The irradiation of the cuvette was carried out in a Luzchem photoreactor equipped with 3 UV lamps.

Triblock polymer
2 mg of the polymer was dissolved in 100 µL of THF.Subsequently, 900 µL of water was introduced to the solution for micelle formation to occur.The dispersion was then filtered with 20 µm pore PTFE filter and transferred to a quartz cuvette for photodegradation.The irradiation of the cuvette was carried out in a Luzchem photoreactor equipped with 3 UV lamps.

Depolymerization and re-polymerization of a copolymer P(DMA-co-C3) Depolymerization
A copolymer P(DMA-co-C3) (Mn 12.5 kg.mol-1,Đ 1.3, incorporation ratio 1.4%) obtained from PET RAFT polymerization of DMA and C3 was dissolved in THF solvent to the concentration of 1 mg.mL -1 .The solution was irradiated with UVB light for 70 min to degrade the polymer via cycloreversion of coumarin cycloadducts embedded in polymer backbone.

Re-polymerization
The resulting degraded polymer solution (containing 6 mg of polymer) was concentrated under reduced pressure over night, yielding a viscous liquid.The degraded polymer was dissolved in water to the concentration of 1.5 mg.mL -1 , followed by irradiation with UVA light.

Synthesis of coumarin cyclic monomer (C3)
Allylic sulfide cyclic monomer bearing coumarin as end groups was synthesized according to our previous publication 7 .

HRMS:
[C53H66O10SNa] + m/z= 917.4269; found: 917.4259, ∆m/z= 1.1ppm  Diacid S4 was synthesized according to modified procedure adapted from 8 .The details of the synthesis can be found in our previous publication 7 .
Synthesis of SC1-SC2 was conducted following the literature-known procedure 9 .

SC1
In a brown round-bottom flask, 4-acetoxystyrene (1.3 mL, 8.5 mmol, 1.2 eq), 1-bromopyrene (2.00 g, 7.0 mmol, 1.0 eq), triphenylphosphine (0.18 g, 0.7 mmol, 0.1 eq), triethylamine (9.7 mL, 70 mmol, 10 eq) were dissolved in dimethylformamide (36 mL) with stirring.The flask was degassed with Ar.After 10 minutes, palladium (II) acetate (90 mg, 0.4 mmol, 0.05 eq) was quickly added to the solution with Ar flowing.The mixture was degassed further for 10 minutes and left stirring at 100 o C for 4 days.The reaction mixture was then diluted with 50 mL of toluene and passed through an alumina column, following by washing with HCl 1M (25 mL x 3).After that, the solution was concentrated under reduced pressure and precipitated in cyclohexane to give yellow precipitate
The mixture was kept stirring at 70 o C for 16 h.After that, an acidic solution (300 mL of water, 7.7 mL of concentrate HCl) was added to the reaction mixture.The precipitate was collected via centrifugation.SC2 was obtained in green-yellow solid.

SC4
Diacid S4 (184 mg, 0.69 mmol, 1 eq), dry dichloromethane (5 mL), oxalylchloride (0.24 mL, 2.75 mmol, 4 eq) were added in an ice cooled Schlenk line flask that connected to Ar gas. 1 drop of dimethylformamide was added to the flask.The mixture was then kept stirring under Ar for 3h.After that, the reaction mixture was brought to room temperature, and the solvent and excess oxalylchloride were removed by vacuum.To the reaction flask, SC3 (1.35g, 2.75 mmol, 5 eq), pyridine (0.28 mL, 3.43 mmol, 5 eq), dry THF (50 mL) were added.The mixture was stirred under Ar for 16 h.To completion, the reaction mixture was concentrated under vacuum, followed by dissolving in dichloromethane to extract with HCl 1N (40 mL x3).The organic phase was then concentrated under reduced pressure and purified by a flash column chromatography with cyclohexane/DCM (98%/2% to 0%/100%) as eluent.The obtained solid was the mixture of SC4 and a small content of SC3.Multiple-time precipitation in methanol removed SC3, affording yellow solid SC4.

SC5
In order to prevent intermolecular cycloaddition reaction, the cyclisation reaction of linear monomer SC4 was conducted at dilute concentration.10 mL solution of SC4 0.5 mg/mL in toluene was degassed with Ar for 20 minutes.Then the solution was irradiated with a LED 465 nm (10W, 1.05 A).The reaction was monitored by SEC at isosbestic point of the photo cycloaddition reaction 355 nm.It was found that the reaction completed after 150 min.The reaction mixture was then concentrated under reduced pressure and freeze dried to remove solvent completely, giving SC5 as a yellow viscous oil.
A control sample which is the polymerization without cyclic polymer was also carried out, yielding a homopolymer PDMA (Mn 19 kg.mol -1 , Đ 1.3, Figure S20 below).Subsequently, these vials were capped and degassed with Argon gas for 8 minutes.The vial was then heated up at 70 o C for different time.To conduct a measurement, the vial was opened to exposure to air for quenching polymerisation.

Experimental setup
The polymerization setup adapted from literature 10 was illustrated in Figure S21 below.Briefly, in a photobox, the well plate of polymerization solution was placed on the top of the LED plate (λmax = 572 nm) as the light source to catalyse the polymerization.The LED plate with the heat sink attached was put in contact with a metal surface (e.g. a heat plate without heating activation) to facilitate heat transfer during polymerization process, preventing overheating the LED plate and well plate.A fan was used to assist the heat reduction of the polymerization system.The LED plate was connected to a power supply which can be tailored to desired current and voltage.The current used in experiment was 0.05A/row of 8 LED bulbs.The polymerization time can be set up by a timer which connects power supply with the electricity power.
The polymer product was precipitated out of dimethyl ether, and dried under reduced pressure.
After that, 10 µL of the polymerization was taken out for SEC measurement.Thus, the remaining amount of CTA (PDMA with RAFT end group) and ZnhTPP in the well plate was 90% of the initial CTA and ZnhTPP amount before beginning the first block polymerization.The fresh DMA monomer (2.34 µL, 22.7 µmol) was then added to the desired ratio of [DMA]/[CTA]=50.Fresh ZnhTPP (1.51 µL of 0.01M in DMSO solution, 0.015 µmol) was added to desired ratio of [ZnhTPP]/[CTA]= 6 %.Cyclic monomer C3 (8.12 µL of 100 mg/mL in DMSO solution, 0.91 µmol, 2 eq) was finally added to the mixture, [C3]/[CTA]=2.Subsequently, the well plate was submitted to PET RAFT polymerization for 20 h.The polymer was precipitated out of diethyl ether and dried under reduced pressure, giving a slight green polymer (Mn 18.5 kg.mol -1 , Đ 1.3).
A control sample which is the polymerization without cyclic polymer and desired ratio of [DMA]/[CTA]=100 in second block was also carried out, yielding a homopolymer PDMA (Mn 22 kg.mol -1 , Đ 1.2, Figure S22 below).

Synthesis of triblock polymer
Diblock polymer containing coumarin dimer in the backbone was synthesized according to the procedure above.
The diblock polymer after workup was dried with Nitrogen gas for 1h to remove diethyl ether solvent.After that, the polymer was dissolved with 70 µL DMF in a glass vial.An aliquot of 3 µL of this solution was used to measure SEC.The remaining 67 µL was used as macro-CTA for chain extension with DMA and SC5 cyclic monomer.With the assumption that all of RAFT agent attended polymerisation reaction to result in polymer with RAFT end group and all polymer was precipitated in diethyl ether, the amount of CTA in this 67 µL solution was 0.43 µmol (5.0 eq).To this solution, DMA (21.9 µL, 213 µmol, 2500.0 eq), AIBN (1.4 µL from stock solution 5 mg/mL in DMF, 0.043 µmol, 0.5 eq), styrylpyrene monomer SC5 (5.2 mg, 4.3 µmol, 50.0 eq) were added.Subsequently, the vial was capped and degassed with Argon for 8 minutes.The vial was then kept at 80 o C for 22 h.After that, the vial was opened to air to stop the polymerisation.The mixture was precipitated with diethyl ether, followed by washing with water to remove unreacted diblock.Finally, the obtained polymer was dried under vacuum, giving a yellow polymer (Mn 40 kg.mol -1 , Đ 1.9).
In conclusion, triblock is estimated to consist of first block of PDMA (101 units), second block of copolymer of DMA and C3 (93 units of DMA, 2 units of C3) and third block of copolymer of DMA and SC5 (499 units of DMA, 6 units of SC5)

Conversion and incorporation ratio in kinetic study of copolymerisation of DMA and SC5
Feed ratio: Molar ratio of SC5/DMA (denoted as F) in feed is calculated from 1 H NMR of polymerisation mixture.Specifically, SC5 is derived from integral of 8 pyrene aromatic proton resonances at 7.8-7.93ppm, and DMA is derived from integral of 1 double bond proton resonance at 6.58 ppm (Figure S29).F=1.6%

Incorporation ratio of copolymer
Incorporation ratio of styrylpyrene cycloadduct groups is calculated from integral of 8 pyrene aromatic protons at 7.8-7.93ppm and integral of 6 protons of PDMA (δ= 2.90 ppm) in the 1 H NMR of the purified copolymer.

𝐼 =
$ !"# 34 C656789:; $ $%& 34 C656789:; where the magnitude of the momentum transfer is defined by:  = %I J sin().Initial model-independent analysis has been performed using Guinier approximation and the power-law fit of the intermediate range of the data.
The middle-range q fits are all in the range of the q -2 , indicating scattering of a Gaussian polymer.Radius of gyration has Rg been estimated using the Guinier approach and calculated directly from a distance distribution function, p(r).
The Guinier approximation allows to estimate the Rg from the low q part of the I(q) as following: & ), qRg < 1 for compact particles.the samples, i.e. position of its maximum and approximate value of the maximum dimension Dmax of the particles.
Figure S30 shows normalised p(r) for all three data sets: Table S3 below summarise estimated values of the Rg and diameter for the three data sets:

Rg, nm Guinier approximation
Rg, nm see eq [2]   Average particle diameter D, nm, see eq [3]   *Dmax (p(r)), nm see eq [1]   P2 *Dmax for these data sets is very sensitive to the choice of the lowest feasible value of q, hence the solution is not always stable, therefore there is a reasonable range presented for the Dmax.
During the modelling, the following parameters have been fixed: sld_solvent and d_penetration (the polymers chains do not penetrate the core).

Figure S 2 .
Figure S 2. Mass spectrum at elution time 19.0 mins acquired from SEC-MS measurement of the copolymer P1 irradiated with UVA 30 min.

Figure S 3 .
Figure S 3. A zoom in of mass spectrum of retention time 19.0 min for degraded copolymer of styrylpyrene monomer SC5 and DMA (upper) and the simulated for doubly charged sodiated oligomer ion with 22 DMA unit and expected styrylpyrene end groups (lower), showing good agreement between found m/z and simulated m/z.

Figure S 4 .
Figure S 4. Left: Stacked 1 H NMR spectra of homopolymer PDMA, cyclic monomer C3 and diblock copolymer P2 (PDMA-b-P(DMA-co-C3)) in CDCl3 (for a full assignment of C3 see Fig. S13); Right: DOSY NMR of polymer P2 showing similar diffusion coefficients for coumarin and DMA, indicative of successful chain extension and copolymerization;

Figure S 5 .
Figure S 5. Mass spectrum at elution time 20.45 min acquired from SEC-MS measurement of copolymer P2 irradiated with UVB 30 min.

Figure S 6 .
Figure S 6.A zoom in of mass spectrum of retention time 20.45 min for degraded diblock copolymer of coumarin monomer C3 and DMA (upper) and the simulated for doubly charged sodiated oligomer ion with 26 DMA unit and expected coumarin end groups (lower), showing good agreement between found m/z and simulated m/z.

Figure S 8 .
Figure S 8. Left: Overlay of RI trace and UV (l = 360 nm) trace in SEC measurement of P3 and distribution of dead chains of second block obtained from subtraction of RI trace to UV (l = 360 nm) trace.Right: the peak area integrated from respective peaks.The amount of dead chain of second block to chain extension product-triblock P3 is calculated from peak area of dead chain peak and UV trace peak.

Figure S 9 .
Figure S 9. Comparison of photodegradation of diblock polymer P2 in DMAc solvent and in water: reduction of averaged molecular weight (Mn) of polymer represented by ratio of Mp of polymer at t min UVB irradiation to Mn of pristine polymer plotted vs UVB irradiation time.

Figure S 10 .Figure S 11 .
Figure S 10.A dispersion of diblock copolymer P2 in water (1.5 mg mL -1 ) was irradiated with UVB for 90 min.Derived count rate of dispersion plotted vs UVB irradiation time (left), hydrodynamic diameter distribution by volume of the dispersion at UVB irradiation time 0 min, 30 min (middle), and hydrodynamic diameter distribution by intensity of the dispersion at UVB irradiation time 0 min, 30 min (right).

Figure S 12 .
Figure S 12. Degradation of P3 in water (2 mg.mL -1 ) under UV irradiation: A) Hydrodynamic diameter distribution by volume of the dispersion with UVA and UVB irradiation obtained via DLS; B) Hydrodynamic diameter distribution by intensity of the dispersion with UVA and UVB irradiation obtained via DLS; C) Derived count rate of dispersion plotted vs UV irradiation; D) overlay SEC of P3, P3 dispersion irradiated with UVA 20 min, and UVA 60 min-UVB 30 min ; E) Overlay SEC traces of the polymer obtained from UVA-UVB irradiation of P3 dispersion in water and 30-min UVA irradiation of its solution in DMAc.

MESTRENOVA 11 .
0 was used.The signals were quoted as follows: s = singlet, bs = broad singlet, d = doublet, t = triplet, dd = doublet of doublets and m = multiplet.Diffusion Ordered Spectroscopy (DOSY) NMR experiments based on 1H-NMR were performed at 35°C on a Bruker 400 Advance III HD spectrometer equipped with either BBO or Quattro Nucleus Probes (QNP) (5mm) with z-gradients (1H: 400.16 MHz).A sequence with longitudinal eddy current delay (LED) using bipolar gradients (Bruker ledbpgp2s) was employed in order to compensate for eddy currents.The diffusion gradient length δ and diffusion delay Δ were determined separately for each sample.Gradient strength was linearly incremented from 2% at 0.96 Gcm-1 to 95% at 45.7 Gcm-1 in 20 steps.The obtained data was processed with TopSpin 4.0.6 and Dynamics Center 2.5.3.After Fourier transformation of the 1D spectra, the signal decay with respect to gradient strength G was fitted to: with γ = gyromagnetic ratio of 1 H and I0 = full signal intensity.

Figure S 18. 1 H
Figure S 18. 1 H NMR spectrum of SC3 acquired in CDCl3.

Figure S 19. 1 H
Figure S 19. 1 H NMR spectrum of SC4 acquired in CDCl3.

Figure S 23 .
Figure S 23.Illustrative representation of experimental setup of PET-RAFT polymerisation experiment (left) and picture of actual setup (right)

Figure S 25 . 6 . 2 .
Figure S 25.Illustrative representation of the degradation of copolymer P1 DMA-co-SC5.As illustrated in above Figure, if all 3 styrylpyrene cycloadducts undergo cycloreversion reaction under UVA irradiation, each P1 chain will disintegrate into 3+1=4 comparable fragments, assuming the even distribution of photoresponsive group in polymer chain.Hence, after complete degradation, Mn of the polymer will be:

Thus,!" $%& 7 × 1 6. 3 .
Figure S 27.Illustrative representation of the degradation of diblock copolymer P2 PDMA-b-(DMA-co-C3) Based on Mp of polymer, estimated structure of diblock P2: DMA111-b-(DMA103-co-C32).As illustrated in above Figure, if all 2 coumarin cycloadducts undergo cycloreversion reaction under UVA irradiation, each P2 chain will disintegrate into 2+1=3 fragments.The largest fragment is the one connected to the nondegradable first block and contains only half of the coumarin cycloadduct monomer.Assuming coumarin cycloadduct distributes evenly in the second block of P2, if disregards the first block in largest fragment, number of DMA units is equal for each fragment.Hence if P2 is fully degraded, Mp of the product (mass of largest fragment) will be:

Figure S 29 . 7 ×
Figure S 29.Illustrative representation of the degradation of triblock copolymer P3 PDMA-b-(DMA-co-C3)-b-(DMA-co-SC5) Based on Mp of polymer, estimated structure of triblock P3: DMA101-b-(DMA93-co-C32)-b-(DMA499-co-SC56).The estimated Mp of the third block thus is 56673 g.mol -1 .The full photodegradation of a copolymer equal to the third block would give 7 fragments with mass reduced to 8096 g.mol -1 (see section 6.1.b).This fragment is still smaller than the first block of P3.Therefore, if the full degradation of P3 will give the largest fragment similar to that from the full degradation of the diblock.Hence if P3 is fully degraded, Mp of the product (mass of largest fragment) will be:

$=Figure S 30. 1 HFigure S 31. 1 H
Figure S 30. 1 H NMR spectra of polymerisation mixture at 0 min in kinetic study experiment (acquired in CDCl3).Conversion of DMA monomerConversion of DMA monomer is calculated from integral of 1 double bond proton of DMA at 6.58 ppm and integral of 6 methyl protons of PDMA (δ= 2.90 ppm) in 1 H NMR of crude polymerisation product.The integral of methyl protons of PDMA is derived from subtraction of integral of DMF solvent and unreacted DMA monomers which are derived from integral of carbonyl proton of DMF and integral of double bond proton of DMA, respectively.

Figure S 32. 1 H
Figure S 32. 1 H NMR spectra of purified copolymer obtained from kinetic study experiment at polymerisation time of 60 min (acquired in CDCl3).Integral of dimethyl proton in PDMA (δ= 2.9 ppm) is obtained from subtraction of integral of DMF protons.Conversion of SC5 monomerConversion of SC5 (CSC5) is calculated from conversion of DMA(CDMA), feed ratio (F) incorporation ratio of SC5 to DMA in copolymer (I) as follows:

Figure S 33 .
Figure S 33.Scattering intensity, I(q) plotted versus momentum transfer q obtained from SANS experiments of diblock polymer P2dispersion in water irradiated with UVB light for 0 min, 30 min and 90 min and their fit performed by SasView with model Power-Law for the middle-range range of the data.Note that the data and fit of P2 irradiated with UVB 30 min and 90 min are offset for clarity by 10 and 100, respectively.

Figure S 35 .
Figure S 35.Normalised p(r) for all three data sets.

Table S 1
. Table representing simulated mass to charge ratio m/z (the most abundant peak) of expected DMA oligomers with different numbers of DMA repeat units (chemical structure depicted in figureS3(bottom)) and m/z found in the actual mass spectrum of photodegraded copolymer of styrylpyrene monomer and DMA (figure 3D in main manuscript), and their mass deviation.

Table S
2. Table representing simulated mass to charge ratio m/z (the most abundant peak) of expected DMA oligomers with different numbers of DMA repeat units (chemical structure depicted in figureS7(bottom)) and m/z found in the actual mass spectrum of photodegraded diblock copolymer of coumarin monomer C3 and DMA (figure 6D in main manuscript), and their mass deviation.

Table S 3
. Summary of estimated values of the Rg and radii for the three data sets.